As is well known by those skilled in the art, forming selected stresses in the channel regions of CMOS devices will enhance performance of the device. For example, parallel tensile stress in the channel region improves performance of an N-FET, whereas parallel compressive stress in the channel region enhances the performance of a P-FET.
Various techniques for creating the desired stress in the N-FET and P-FET portion of the CMOS device have been suggested. For example, Ghanni, et al., in a paper entitled “A 90 nm High Volume Manufacturing Logic Technology Featuring Novel 45 nm Gate Length Strained Silicon CMOS Transistors” (2003 IEDM, 11.6.1-11.6.3), discusses a post salicide “highly tensile” silicon nitride capping layer wherein the stress is transferred to the NMOS channel through the source/drain regions. A layer thickness of approximately 75 nm results in a 10% NMOS IDSAT gain.
U.S. Patent Publication 2004/0113217 A1 to Chidambarraco, et al. discloses a method of causing tension and/or compression on a substrate by the selection of an “L-like”shaped layer of material formed adjacent sidewalls of a gate structure that is disposed above the channel regions. The “L-like” shaped layer of material is formed so that the two legs of the material are adjacent both the gate sidewalls and the substrate of the device such that stresses are formed on adjacent substrate areas. In addition, the material of the “L-like” shaped layer is selected so that the stresses are controlled or varied as necessary within both the N-FET and P-FET devices to improve the IC performance.
Papers by Y. Kim, et al. (2003 VLSI, pp. 639) and T. Iwamato, et al. (2003 IEDM, pp. 167) also disclose the use of “L-like” shaped SiN film and HfSiO or oxynitride gate dielectrics.
All of the above techniques provide some improvements to the performance of a CMOS device by inducing stress in the channel regions of the device. However, further increases in the performance of the device by further increasing the stress that can be induced in the channel regions would be advantageous.